The invention relates to a device for comminuting dry ice granules, comprising a housing having a flow channel for dry ice granules which can be applied, by means of compressed gas, to a surface to be cleaned, and also comprising a first comminution member for comminuting the dry ice granules which are to be dispensed.
The invention also relates to a dry ice dispensing arrangement for dispensing a mixture of compressed gas and dry ice granules, having a device of the foregoing kind.
DE 10 2004 045 770 B3 discloses a dry ice spraying device for providing a mixture of compressed gas, preferably compressed air, and dry ice. In order to supply the compressed gas, the dry ice spraying device can be connected to a compressed gas source. The dry ice spraying device comprises a reservoir of dry ice and a metering device by which the dry ice can be mixed with the compressed gas. The dry ice is stored in the form of dry ice granules (so-called “pellets”), which are usually the size of grains of rice, and are introduced into the flow path of the compressed gas by means of the metering device, as a result of which said dry ice is mixed with the compressed gas. A dry ice dispensing unit which can be connected to the dry ice spraying device can be used to subject, for example, a surface to be cleaned to the action of pressurized dry ice granules. Contaminants which adhere to the surface are intensely cooled by the action of dry ice granules, as a result of which they become brittle and are detached from the surface. The dry ice granules which strike the surface sublimate on impact, that is to say pass directly from the solid state to the vapor state, and in the process assist in detaching contaminants adhering to the surface.
The devices cited in the introduction for comminuting dry ice granules (so-called “scramblers”) are usually sold as accessory units for dry ice dispensing arrangements. In order to comminute dry ice granules, said devices comprise a flow channel through which the mixture of compressed gas and dry ice granules flows and on which a comminution member is disposed. If the dry ice granules which are mixed with compressed gas strike the comminution member, said dry ice granules can break up and as a result be comminuted. Consequently, the comminuted pellets are of smaller average size at the output end of the device than at the input end of the device. The dry ice granules comminuted in this way are suitable, for example for preferred cleaning of sensitive surfaces, fine structures or undercuts.
Generic devices for comminuting dry ice granules are known, in which devices the housing comprises a tube that surrounds the flow channel and into which a comminution member in the form of a metal wire is welded. This is complicated in terms of production and, furthermore, the wire is subject to a high level of wear.
In the case of other types of generic devices for comminuting dry ice granules, the comminution member is in the form of a grating mesh and is inserted into a tube which is surrounded by the housing. In such devices, there is a risk of the grating mesh becoming clogged up with dry ice granules during operation, so that the flow channel becomes blocked.
Furthermore, the two devices for comminuting dry ice granules described above encounter the problem that the degree of comminution of dry ice granules, that is to say the ratio of the average size of the pellets at the input end of the device to the average size of the pellets at the output end of the device is inalterable.